Detailed analysis of Apple A6 core reveals layout done by hand

X-ray micrographs also confirm 32nm high K process.

Over the last week, more and more details of Apple's custom A6 processor design have come to light, including a custom armv7s-compatible core design and its triple-core GPU. Detailed analysis by Chipworks and iFixit have revealed that Apple's custom ARM core design appears to have been laid out by hand instead of by computer algorithms—a time-consuming process that can result in optimized high-frequency operation.

Engineers at Chipworks used ion beam etching to remove all the casing material from the A6's die, and then used a variety of high-powered microscopes to peer into its structure. The detailed layout of the dual ARM cores isn't typical of integrated circuits that are increasingly laid out using software, instead suggesting an approach that is becoming more rare in today's microprocessors.

"It looks like the ARM core blocks were laid out manually—as in, by hand," iFixit's Miroslav Djuric said via e-mail. "A manual layout will usually result in faster processing speeds, but it is much more expensive and time-consuming."

"The manual layout of the ARM processors lends much credence to the rumor that Apple designed a custom processor of the same caliber as the all-new Cortex A15," according to Djuric, referring to its compatibility with the more advanced armv7s architecture also used by the Cortex A15. The previous A5 design used a tweaked Cortex A9 core, which is less powerful at the same clock speed than either the A6 or the Cortex A15 and uses the less-capable armv7 architecture.

That time-consuming manual layout process would also certainly help explain why it took Apple over four years from its acquisition of fab-less design firm PA Semi to release its own custom silicon for its mobile devices. Based on our experience with the iPhone 5, the hard work is paying off in spades.

The overall A6 die area is 96.71mm2, compared to approximately 70mm2 for the 32nm variant of the A5 processor. A close look at a cross-section of the A6 confirms that it is also built on Samsung's 32nm high-K process, giving Apple extra area for additional functional blocks, like the dedicated image signal processor and extra GPU core.

I don't see how they can state that the ARM cores were laid out by hand. Some parts of the chip, it absolutely would make sense to lay it out by hand. There is order in data flow that humans are better at designing than algorithms are. Random control logic, however? There really is no benefit to having a human manually laying out every last logic gate. In fact, it is counter-productive.

It can certainly be that large portions are laid out by hand. People want to make order from chaos, so they will generally see and be drawn to that order first. But I suspect that further investigation will show computer synthesized portions, as well.

What you see in that image is the equivalent of looking down at Los Angeles from 10,000 feet. Even with a telescope, you would be hard pressed to analyze the entire city in such a short period of time because there is so much to look at.

For very complicated chips like this, I'm pretty sure this is typical. Computer algorithms can only get you so far. Sometimes they can end up with really weird layouts, too.

From the article:

"The manual layout of the ARM processors lends much credence to the rumor that Apple designed a custom processor of the same caliber as the all-new Cortex-A15, and it just might be the only manual layout in a chip to hit the market in several years."

"The manual layout of the ARM processors lends much credence to the rumor that Apple designed a custom processor of the same caliber as the all-new Cortex A15," according to Djuric, referring to its compatibility with the more advanced armv7s architecture also used by the Cortex A15.

Then in the very next sentence:

Quote:

The previous A5 design used a tweaked Cortex A9 core, which is less powerful at the same clock speed than either the A6 or the Cortex A15 and uses the less-capable armv7 architecture.

So how can the armv7 architecture be simultaneously "more advanced" and "less-capable" ?

I know nothing about ARM, was the first mention supposed to be "armv8", or the second mention supposed to be "armv6", or something else entirely?

For those of us that didn't graduate with an EE, can someone explain in sufficient detail *how* a hand made layout is better? I assume it has something to do with how the data will flow through the core, ensuring that each subsequent step through the process has to travel the least amount of distance and such...or am I way off?

"The manual layout of the ARM processors lends much credence to the rumor that Apple designed a custom processor of the same caliber as the all-new Cortex A15," according to Djuric, referring to its compatibility with the more advanced armv7s architecture also used by the Cortex A15.

Then in the very next sentence:

Quote:

The previous A5 design used a tweaked Cortex A9 core, which is less powerful at the same clock speed than either the A6 or the Cortex A15 and uses the less-capable armv7 architecture.

So how can the armv7 architecture be simultaneously "more advanced" and "less-capable" ?

I know nothing about ARM, was the first mention supposed to be "armv8", or the second mention supposed to be "armv6", or something else entirely?

"The manual layout of the ARM processors lends much credence to the rumor that Apple designed a custom processor of the same caliber as the all-new Cortex A15," according to Djuric, referring to its compatibility with the more advanced armv7s architecture also used by the Cortex A15.

Then in the very next sentence:

Quote:

The previous A5 design used a tweaked Cortex A9 core, which is less powerful at the same clock speed than either the A6 or the Cortex A15 and uses the less-capable armv7 architecture.

So how can the armv7 architecture be simultaneously "more advanced" and "less-capable" ?

I know nothing about ARM, was the first mention supposed to be "armv8", or the second mention supposed to be "armv6", or something else entirely?

From what I understand, the armv7s architecture is more capable than the armv7 one.

Sometimes I feel bad for Apple's engineers. The internet explodes with the ignorant masses calling them lazy and their work boring and non-innovative. Meanwhile they're milking power out of custom processors by hand in order to best chips with higher clocks and twice the cores. They have a neat tech solution to cabling that is as tiny and future proofed as possible. They have the highest quality smartphone display ever on a new in-cell touch process.

And that's just a few of the components in an entirely revamped phone with a lighter, smaller-volume enclosure. And that's to say nothing about the scale at which they're going into production.

But all they did was make the screen a little taller, who cares, amirite? I don't know if it's willful ignorance or another sign of the failure of the educational system in the US, but I hope engineering survives in the end regardless.

Sometimes I feel bad for Apple's engineers. The internet explodes with the ignorant masses calling them lazy and their work boring and non-innovative. Meanwhile they're milking power out of custom processors by hand in order to best chips with higher clocks and twice the cores. They have a neat tech solution to cabling that is as tiny and future proofed as possible. They have the highest quality smartphone display ever on a new in-cell touch process.

And that's just a few of the components in an entirely revamped phone with a lighter, smaller-volume enclosure. And that's to say nothing about the scale at which they're going into production.

But all they did was make the screen a little taller, who cares, amirite? I don't know if it's willful ignorance or another sign of the failure of the educational system in the US, but I hope engineering survives in the end regardless.

The thing is that, I don't think so many people are reading those kind of articles. It's easier to support/critisize a brand/product without having a deep knowledge of how it is made and why it might be so good/terrible.

That's also why I'm glad we have arstechnica to keep us informed on such geeky subjects ^^ .

To be fair, the iPhone 5 announcement article brought out the trolls in force. Almost every post on that article was trolls trolling other trolls in a big circle. All of the reasonable people bailed out immediately when it became clear that the trolls owned the article.

swarmster: I guess the problem there is that not all of their engineers are created equal.

Apple's become so large that there's bound to be a large variance in the sort of stuff they create. On one hand, you have a team within Apple that's capable of creating something like this. On the other, you have the group responsible for Apple Maps as initially launched with iOS 6.

This is really interesting, but since I know basically nothing about chip architecture, I'm afraid it's mostly lost on me. I think I might spend the rest of my day educating myself to gain an understanding and appreciation for the hard work that evidently went into this.

Duncan MacLeod wrote:

Laroquod wrote:

*sniffs deeply*

Smells like bullshit.

[citation needed] or at least, ya know, an argument?

A quick review of his posting history reveals an ideal chance to test the new ignore feature.

Sometimes I feel bad for Apple's engineers. The internet explodes with the ignorant masses calling them lazy and their work boring and non-innovative. Meanwhile they're milking power out of custom processors by hand in order to best chips with higher clocks and twice the cores. They have a neat tech solution to cabling that is as tiny and future proofed as possible. They have the highest quality smartphone display ever on a new in-cell touch process.

And that's just a few of the components in an entirely revamped phone with a lighter, smaller-volume enclosure. And that's to say nothing about the scale at which they're going into production.

But all they did was make the screen a little taller, who cares, amirite? I don't know if it's willful ignorance or another sign of the failure of the educational system in the US, but I hope engineering survives in the end regardless.

It's probably worth taking into consideration how much of a difference it makes. If they spent four years on optimizations that will be caught up with by three months of cpu progress, then the work they've done isn't very worthwhile. Being lazy and smart is better than working hard and stupid.

There is difference between "hand crafting" the circuitry, and manual layout. If the design is based on an "abstration", say VHDL, you get an amazingly dense mess of random logic via software. Multiple layers of metal make computer generated wiring nearly as goog as hank packed layout. This assumes a standard cell approach for the random logic.

If you hand craft the design, as opposed to standard cell, you can often reduce the size of the circuitry. For instance, use smaller gates if you don't need the fan out (that is drive a large number of gates.) In order for testability, typical flip flops used with silicon compilation have the ability to be preset. This adds extra transistors. If you design fault coverage vectors (testability) by hand, or some means that doesn't need all the preset flip flops, you can get a smaller design.

Generally hand packing isn't going to save a lot of space if you have a large number of metal layers. It won't make the design significantly faster since the interconnect is metal. In the early 90s, where maybe you had to use poly interconnect as one of the layers, then hand packing was valuable.

When the dust settles, using a smaller process nearly always wins the speed/power race.

What makes this article seem dubious at best is if you spend 5 years designing a chip, the silicon process at the start of the design will be obsolete. The design rules for the new process will be different, so there goes your hand packing theory.

"It looks like the ARM core blocks were laid out manually—as in, by hand," iFixit's Miroslav Djuric said via e-mail. "A manual layout will usually result in faster processing speeds, but it is much more expensive and time-consuming."

Well, doesn't the A6 run on not so remarkable speeds to save power? So the question is what does this hand layout to power consumption?

I thought power consumption is mostly dependent on the geometry and leakage of the transistor/process tech used. Is it also dependent on the chip layout? How? I'm dying to learn more.

Sometimes I feel bad for Apple's engineers. The internet explodes with the ignorant masses calling them lazy and their work boring and non-innovative. Meanwhile they're milking power out of custom processors by hand in order to best chips with higher clocks and twice the cores. They have a neat tech solution to cabling that is as tiny and future proofed as possible. They have the highest quality smartphone display ever on a new in-cell touch process.

And that's just a few of the components in an entirely revamped phone with a lighter, smaller-volume enclosure. And that's to say nothing about the scale at which they're going into production.

But all they did was make the screen a little taller, who cares, amirite? I don't know if it's willful ignorance or another sign of the failure of the educational system in the US, but I hope engineering survives in the end regardless.

Arguably the "best" display.

And it's all very good having a fast CPU.

It's a bit shit when you're lost because the mapping solution provided is absolute wank compared to previous.

Oh, don't get me wrong, I'm not detracting from the guys involved in the CPU.

I'm talking about Apple as a whole.

Like making sure their $30 cables are all ok, but maps isn't.

Stop thinking the sun shines out of Apples arse, it most certainly does not.

For those of us that didn't graduate with an EE, can someone explain in sufficient detail *how* a hand made layout is better? I assume it has something to do with how the data will flow through the core, ensuring that each subsequent step through the process has to travel the least amount of distance and such...or am I way off?

You've pretty much nailed it...

Apple did not layout every transistor by hand... they organized the blocks to make for optimal signal path lengths in the chip to make it more efficient.

Anyone who has any experience with auto-routing for something even as crude as circuit board layout knows that the layout algorithms will only get you so far. Sometimes the machine makes correct, but ultimately inefficient choices. This can lead to things like unwanted signal coupling in the design and lower the ultimate performance potential of the part.

There is not one company on this planet that is laying out, say, a memory cache by hand. Anything that is patterned like that is done by machine. Connecting the dots, on the other hand, is a very subjective thing and it may be done in one fashion for a particular application and/or another for something else.

But all they did was make the screen a little taller, who cares, amirite? I don't know if it's willful ignorance or another sign of the failure of the educational system in the US, but I hope engineering survives in the end regardless.

I don't think it has anything to do with education, more likely people defending their allegiance to a particular brand etc. and having irrational disdain for competing products. There is nothing wrong with liking what you like but you have to look big picture. I like my iPhone, love my new 5, but would it be where it is today w/o competition? I mean if there never was Android and all Apple had to worry about was RIM and WinMobile all these years you think we'd be looking at an Apple that was doing cool, and very very expensive, stuff like hand tuning custom SoC's? On the flip side if there was never an iPhone do Android peeps think Android would be what it is today? I may like Apple but I like advancement and new toys better, even if I might not be apt to buy an Android based handset it doesn't mean I don't see their role in improving the breed.

They have the highest quality smartphone display ever on a new in-cell touch process.

Thank LG and Sharp

swarmster wrote:

And that's just a few of the components in an entirely revamped phone with a lighter, smaller-volume enclosure. And that's to say nothing about the scale at which they're going into production.

Thank Foxconn

I'm sorry, but...why? It's Apple's engineers' names on this 2007 patent for in-cell touch LCDs. I find it even harder to believe that Foxconn designed a method for using diamonds to cut and polish for chamfers in a way that repeatable for 100 million devices, or how to seamlessly integrate a sapphire crystal into glass. Just like how Foxconn wasn't the ones that designed a method for cutting invisible holes in MacBooks with semiconductor manufacturing lasers, so that your iSight status LED can't be seen when off.

Personally, I will thank the engineers, despite everyone's efforts to discredit the field lately.

At least in this case, they're not doing anything all that new or innovative though. At least, nothing's been released says it is.

From what I can gather, most chip manufacturers do this and have been doing these hand layouts for a decade at least. Its just news because... well someone decided to write an article about it. But if you read carefully, Ars was pretty careful not to act like this was something new or different either. Just time consuming. They wrote that over and over.

It's a bit shit when you're lost because the mapping solution provided is absolute wank compared to previous.

Because, you know, its *absolutely* *impossible* to visit 'maps.google.com' in Safari on the phone, tap the 'send to' button, and select 'Add to home screen'. Oh, wait, no it's not. I just did it in about 3 seconds.

At least in this case, they're not doing anything all that new or innovative though. At least, nothing's been released says it is.

From what I can gather, most chip manufacturers do this and have been doing these hand layouts for a decade at least. Its just news because... well someone decided to write an article about it. But if you read carefully, Ars was pretty careful not to act like this was something new or different either. Just time consuming. They wrote that over and over.

Two things...- Nitpicking, NP-complete means not solvable quickly; it doesn't mean unsolvable.- Many (most?) NP-complete problems have existing almost-ideal solutions which are very fast, and get results that are extremely close to optimal (or hit the optimal case a large percentage of the time, but it's intractably difficult to prove that a better solution does not exist)